I find the concept interesting, and that nobody protested against it. Is it because so much time passed between Lincoln and today? I could imagine that if you do "Barack Obama: Vampire Hunter" and maybe let him run around like Blade that you'd get criticized into oblivion.
Eh. Being "criticized" also means you're being paid attention to, and generating publicity that will reach a potentially paying audience.
I'm sure some uptight historians have already complained about the book on which it was based, but how many people care what uptight historians, or any type of historians, have to say about their entertainment choices? If I were doing PR for this movie, I'd have some really uptight historians lined up to start bitching about how unseemly the movie is.
Doing a supernatural-horror movie with real life current public figures in it is an interesting idea. I doubt Obama, being a public figure, could sue for libel. Anyway, if he's the good guy, what's the problem? We can always say Republicans = vampires, and it's a political allegory. (With that hair, Mitt would make a fantastic bloodsucker and I'm 99% sure Santorium is already one.)